In the conventional therapeutic protein-based industry, recombinant cells are expanded and induced to produce target proteins, which are then isolated and purified before final formulation in chilled excipient designed to stabilize proteins. In such application, maintaining proteins in uniform suspension in the final fill/finish step is not a great concern, largely due to the fact that proteins do not settle very fast in the excipient relative to the time required for processing to create noticeable concentration gradient.
On the other hand, in the growing field of cell therapy where animal cells in their native pluripotent, induced pluripotent, and/or differentiated form would be cultured and expanded, the cells themselves are the final product that must be isolated and dispensed into final vials. Maintaining cells in uniform suspension in the excipient during the dispensing step is more critical and challenging compared to maintaining proteins in suspension. Although there are a number of ways to dispense such cells in the art, such as withdrawing cells with a pipette from above, none as yet has been able to repeatedly and accurately dispense cultured cells from a vessel on demand.